Non-aqueous electrolytic battery and its manufacturing method

ABSTRACT

A nonaqueous electrolyte battery with a higher energy density in which a useless part which has no contribution to the electromotive is reduced, and a method for manufacturing the same are provided. A positive electrode laminate ( 5 ) (a positive electrode) having a positive active material layer ( 2 ) is located in a first area which extends from an approximate center part ( 7 ) to one end on one of both sides of a separator  1 , and a negative electrode laminate ( 6 ) (a negative electrode) having a negative active material layer ( 3 ) is located in a second area which extends from the approximate center part ( 7 ) to the other end on the other side which is opposite to the side having the first area of the separator ( 1 ). The separator ( 1 ) having the positive electrode laminate ( 5 ) and the negative electrode laminate ( 6 ) thereon is wound around the approximate center part ( 7 ) to constitute a wound electrode ( 4 ).

BACKGROUND OF THE INVENTION

The present invention relates to a nonaqueous electrolyte battery and amethod for manufacturing the same.

In recent years, many portable electronics devices, such as videocameras, electronic notebooks, and laptop computers (portable personalcomputers), become widespread, and are developed in terms of highperformance, miniaturization and weight saving, and portability. Smalllight batteries with a high capacity have strongly been required as aportable power supply for these electronics devices. On the other hand,demands of secondary batteries, which can be recharged and repeatedlyused, have been increasing, instead of primary batteries which are usedonce and thrown away after discharging.

Conventional secondary batteries which have generally been used are anickel cadmium (NiCad; NiCd) battery using an alkali electrolyticsolution, a lead storage battery and the like. However, the limit of adischarge voltage per cell in these conventional secondary batteries isabout 1.2 V. Although various research and developments have beenprogressing to accomplish further improvements in their dischargecapacity, output voltage, and the like, the improvements in theperformances seem to reach the limit. It is practically difficult tofurther improve the energy density, and to accomplish the properties ofthe miniaturization, the weight saving, and high capacity in thenickel-cadmium battery, the lead storage battery, and the like. Also aself-discharge rate at normal temperatures in the nickel-cadmiumbattery, lead storage battery, and the like is generally as high as 20%or more in one month. If the batteries are charged once, left during acertain period, and then used again, an apparent discharge amountthereof is decreased due to a natural discharge, and controlling thecharge amount becomes complicated, for example, an additional charge isneeded before reusing the batteries, which are disadvantages.

Then, nonaqueous electrolyte secondary batteries such as a lithium ionsecondary battery with excellent properties have been investigated. Inthese batteries, a nonaqueous solvent is used as an electrolyticsolution, and a light metal such as lithium is used as a negativeelectrode. This provides the excellent properties: a discharge voltageof 3.7 V or more which is about three or more times of the conventionalNiCd battery; a high discharge voltage property resulting in a highenergy density; and a low rate of self-discharge. The lithium ionsecondary battery is greatly expected to be used as a power supply forelectronics devices such as electronic watches used continuously for along period, backup power supplies for continuously storing data invarious memory devices like D-RAM (Random Access Memory), calculators,cameras, and radios in addition to the above portable electronicsdevices like the laptop computers which requires a high capacity and along-term charge cycle life.

Moreover, various shapes have been proposed for the lithium ionsecondary battery, and thin batteries such as a sheet type battery witha thin large area, and a card type battery with a thin small area areexpected to be preferably applicable to various electronics devices witha thinner shape. For example, batteries using a gel-type solidelectrolyte in which an electrolyte is impregnated with a matrixpolymer, and using a conductive organic macromolecule as a solidelectrolyte are suggested for the thin battery. In these batteries usingthe solid electrolyte, a wound electrode is formed into a flat shape,and covered with an exterior material obtained by composing andlaminating, for example, a polyethylene film and aluminum foil. It isexpected that this can accomplish a thinner form, weight saving, and ahigher energy density compared with the conventional batteries.

On the other hand, it is desired to accomplish much higher energydensity in the lithium ion secondary batteries, but this requiresfurther decreasing useless parts which do not contribute toelectromotive in the wound electrode.

However, the thin batteries as described above has inherently a smallthin outsurface dimension, so it is very difficult to further decreasethe useless parts which do not contribute to the electromotive in theconventional nonaqueous electrolyte batteries which comprise the woundelectrode composed of a positive electrode, a negative electrode, and aseparator which are bonded, or laminated, and spirally wound, which is aproblem.

Especially, in the conventional way, the positive electrode, thenegative electrode, and the separator are simply laminated, and theseparator should be wound many times to form a core of the woundelectrode which is positioned approximately in a center part(approximate center part) of the wound electrode, or a core materialshould be used approximately in the center part. It is actually verydifficult or impossible to eliminate these processes. For this reason,the core, which is composed of at least an end of the separator beingwound several times, and the core material occupy a space which has nocontribution to the electromotive, but they cannot be reduced noreliminated. This also prevents the improvement in the energy density.

Moreover, the conventional wound electrode, which is formed by simplybonding the positive electrode, the negative electrode, and theseparator to form an electrode laminate, and winding the laminate aroundthe core or the core material, has a sloping shape with a cross part ofa circle, an ellipse which is more circular, an oval, or a rhombus, andis less likely to be formed into a flat shape. Therefore, the woundelectrode should be pressed from the upper and lower surfaces thereofand formed into a flat type one which is applicable to the thin battery.However, the original wound electrode has a shape like a cylinder, sounfortunately, distortion and stress in terms of strength of materialeasily occur in a process of forming it into the flat type with an eventhickness.

The present invention has been achieved in view of the above problems.It is an object of the invention to provide a nonaqueous electrolytebattery with a higher energy density in which a useless part which hasno contribution to the electromotive is reduced. Moreover, it is anotherobject to provide a method for manufacturing a nonaqueous electrolytebattery which produces easily such a nonaqueous electrolyte battery.

SUMMARY OF THE INVENTION

A nonaqueous electrolyte battery according to the present inventioncomprises: a wound electrode where one separator, a positive electrodehaving a positive active material layer, and a negative electrode havinga negative active material layer are wound; and a nonaqueous electrolytewith which at least the separator is impregnated, wherein the woundelectrode has a structure where the positive electrode having thepositive active material layer is located in a first area which extendsfrom an approximate center part to one end on one of both sides of theseparator, the negative electrode having the negative active materiallayer is located in a second area which extends from the approximatecenter part to the other end on the other side of the separator, and theseparator having the positive electrode and the negative electrodethereon is wound around the approximate center part. Here, the above“one substantially seamless separator” means that the separator used forthe nonaqueous electrolyte battery according to the invention includesnot only one completely jointless separator but also one piece composedof two or more separators are connected each other, one sheet composedof two separators which are connected end to end, for example, with aadhesive tape, and the like.

Moreover, a method for manufacturing a nonaqueous electrolyte batteryaccording to the present invention is used for manufacturing anonaqueous electrolyte battery which comprises a wound electrode whereone substantially seamless separator, a positive electrode having apositive active material layer, and a negative electrode having anegative active material layer are wound, and a nonaqueous electrolytewith which at least the separator is impregnated, and comprises thesteps of: locating the positive electrode having the positive activematerial layer in a first area which extends from an approximate centerpart to one end on one of both sides of the separator; locating thenegative electrode having the negative active material layer in a secondarea which extends from the approximate center part to the other end onthe other side of the separator; and winding the separator which has thepositive electrode and the negative electrode thereon around theapproximate center part to form the wound electrode.

According to the nonaqueous electrolyte battery and the method formanufacturing the same of the present invention, the positive electrodehaving the positive active material layer is located in the first areawhich extends from the approximate center part to one end on one of theboth sides of the separator, the negative electrode having the negativeactive material layer is located in the second area which extends fromthe approximate center part to the other end on the other side of theseparator (that is, an approximate half area on the other end on a sideopposite to the first area in the separator), and the separator havingthe positive electrode and the negative electrode thereon is woundaround the approximate center part to form the wound electrode. A corecomposed of a wound end of the separator, core materials as anothercomponent, and the like are unnecessary.

Additionally, for example, using a flat plate-type jig having a slit, inthe center thereof through which the separator is held, the approximatecenter part of the separator is tightly held through the slit, theseparator is wound and bound around the jig, and the jig is removed fromthe wound electrode after the winding. A flat shape of the woundelectrode has already been obtained in the winding step.

Moreover, when the positive electrode may be composed of the positiveactive material layer being applied to a positive electrode currentcollector, and the negative electrode may be composed of the negativeactive material layer being applied to a negative electrode currentcollector, an part, to which neither positive active material layer nornegative active material layer is applied, may be located at anoutermost periphery of the wound electrode. Thereby, the active materiallayer on the outermost periphery of the wound electrode which has nocontribution to the electromotive is eliminated, and a volume of a partcorresponding thereto is further reduced.

Moreover, a lead electrode may be located in a certain position, whichis on an innermost part near the approximate center part of the woundelectrode, of the positive electrode and/or the negative electrode.Furthermore, the positive electrode may be composed of the positiveactive material layer being applied to the positive electrode currentcollector, and the negative electrode may be composed of the negativeactive material layer being applied to the negative electrode currentcollector, and neither positive active material layer nor negativeactive material layer may be applied to a position of the leadelectrode. Therefore, the part which has substantially no contributionto the electromotive is eliminated, the volume of the above part isfurther reduced, and occurrence of irregularity of the wound electrodedue to the thickness of the lead electrode is prevented.

Moreover, the nonaqueous electrolyte may be a gel-like electrolyte tofurther improve electromotive properties and the discharge capacityitself.

Moreover, the wound electrode may have a structure on which the woundelectrode is covered with an exterior material composed of a shapedlaminate film of a synthetic resin and metallic foil, a positive leadelectrode is connected to the positive electrode, a negative leadelectrode is connected to the negative electrode, and the positive leadelectrode and the negative lead electrode are exposed from the exteriormaterial to the exterior, to obtain a so-called flat type battery whichis preferably used, for example, for cellular phones, the electronicnotebooks, and the like,

Moreover, the separator may have segments which are separated by thecenter part and on which the positive electrode on the first area andthe negative electrode on the second area are respectively laminated,and one end of one of the segments near the approximate center partalmost face with one end of the other segment near the approximatecenter part. In such a case, it is desirable to cover either or both ofthe ends of the segments facing each other in the approximate centerpart of the wound electrode with the separator, an insulating material,or insulating masking tape, in order to prevent the short circuit of thepositive electrode and the negative electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a schematic structure of a wound electrode of alithium ion secondary battery according to an embodiment of theinvention.

FIG. 2 is a view showing a wound electrode and an exterior container forhousing the same.

FIG. 3 is a view showing an appearance of the lithium ion secondarybattery with the wound electrode shown in FIG. 1 according to anembodiment.

FIG. 4 is a view showing a positive electrode laminate used for thewound electrode shown in FIG. 1.

FIG. 5 is a view showing a negative electrode laminate used for thewound electrode shown in FIG. 1.

FIG. 6 is a view showing an example of a jig used for winding theseparator, the positive electrode laminate, and the negative electrodelaminate to produce the wound electrode.

FIGS. 7A to 7D are views showing steps of winding the separator, thepositive electrode laminate, and the negative electrode laminate toproduce the wound electrode.

FIG. 8 is a view showing an example of a jig used for winding aseparator having pre-separated segments with a first area and a secondarea.

FIG. 9 is a view showing the wound electrode produced by winding theseparator having the pre-separated segments with the first area and thesecond area.

FIG. 10 is a view showing a center part of the wound electrode producedby winding the separator having the pre-separated segments with thefirst area and the second area.

FIG. 11 is a view showing an example of a state of generating anelectrical short circuit where an end face of the positive electrodelaminate is attached to an end face of the negative electrode laminatein the wound electrode shown in FIG. 9.

FIG. 12 is a view showing an example of the wound electrode shown inFIG. 9 where the end face of the positive electrode laminate and the endface of the negative electrode laminate are covered respectively withends of the segments of the separator.

FIG. 13 is a view showing an example of the wound electrode shown inFIG. 9 where the end face of the positive electrode laminate and the endface of the negative electrode laminate are covered with an insulatingtape.

FIG. 14 is a view showing an example of substantially one piece of theseparator where two separators are bonded each other.

FIG. 15 is a view showing an example of substantially one piece of theseparator where two separators are bonded each other with an adhesivetape.

FIG. 16 is a view showing an example where a multilayer positiveelectrode laminate, a multilayer negative electrode laminate, and aseparator are wound to form the wound electrode.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail belowwith reference to accompanying drawings.

FIG. 1 is a view showing typically a schematic structure of a woundelectrode of a flat-type lithium ion secondary battery (a nonaqueouselectrolyte battery) according to an embodiment of the invention.

The lithium ion secondary battery has a principal part which consists ofa wound electrode 4 consisting of one substantially seamless separator1, a positive electrode having a positive active material layer 2, and anegative electrode having a negative active material layer 3, and anonaqueous electrolyte (not shown) with which at least the separator 1is impregnated. A positive electrode laminate 5 (the positive electrode)having the positive active material layer 2 is located in a first areawhich extends from an approximate center part 7 to one end on one ofboth sides of the separator 1 (for example, the outside surface). Anegative electrode laminate 6 (the negative electrode) having thenegative active material layer 3 is located in a second area whichextends from the approximate center part 7 to the other end on the otherside (the inside surface) which is opposite to the side having the firstarea (the outside surface). The separator 1 having the positiveelectrode laminate 5 and the negative electrode laminate 6 thereon iswound around the approximate center part 7 using a flat plate-likewinding jig with a slit near a center for holding the separatortherethrough, to constitute the wound electrode 4. A positive leadelectrode 8 and a negative lead electrode 9 are located on the innermostside of the winding of the wound electrode 4. In addition, masking tapes41 a, 41 b, 41 c, and 41 d are located in parts which are assumed to beattached to weld flash of ends of adjoining components and the like.

The wound electrode 4 is housed in an exterior container (an exteriormaterial) 10 as shown in FIG. 2. The exterior container 10 is a shapedlaminate film in which a highly insulating polyethylene film islaminated on both sides of aluminum foil, into a flat container-shape.

Concrete materials of the exterior container 10 will be described asfollows.

The materials shown below can be used as a composition of the laminatefilm, for example. Here, plastic materials to be used therefor areexpressed by the following abbreviated names: polyethyleneterephthalate:PET, molten polypropylene :PP, cast polypropylene:CPP,polyethylene:PE, low density polyethylene:LDPE, high densitypolyethylene:HDPE, linear low density polyethylene:LLDPE, and nylon:Ny.Moreover, AL is the abbreviation for aluminum which is a metallicmaterial used as a barrier film with moisture permeability resistance.

The most general composition is an exterior layer/a metal film/a sealantlayer=PET/AL/PE. Moreover, in addition to this composition, othergeneral laminate film compositions as shown below can be used: aexterior layer/a metal film/a sealant layer=Ny/AL/CPP, PET/AL/CPP,PET/AL/PET/CPP, PET/Ny/AL/CPP, PET/Ny/AL/Ny/CPP, PET/Ny/AL/Ny/PE,Ny/PE/AL/LLDPE, PET/PE/AL/PET/LDPE, and PET/Ny/AL/LDPE/CPP. This is notto say that metals other than AL are applicable as the metal film.

The exterior container 10 has a principal part consisting of a flat lid11 and a container body 12. A periphery part of the flat lid 11 and aflange part around the container body 12 are joined together, and thewound electrode 4 is sealed therein. As shown in FIG. 3, both of thepositive lead electrode 8 and the negative lead electrode 9, whichproject from the wound electrode 4, project out from one end of theexterior container 10. Resin films 14 a and 14 b are located in parts ofthe positive lead electrode 8 and the negative lead electrode 9 whichare between the periphery part of the flat lid 11 and the flange part 13around the container body 12. Finally the flange part 13 is bent toshape the exterior container 10 into a flat box-shape appearance asshown in FIG. 3.

In more detail, as shown in FIG. 4, the positive electrode laminate 5 isformed by applying the positive active material layer 2 containing apositive active material to both sides of a positive electrode currentcollector 15.

Aluminum foil and the like can preferably be used as the positiveelectrode current collector 15, for example. It is desirable to useporous metal foil as the metallic foil, because this can furtherincrease bond strength and a contact area between the positive electrodecurrent collector 15 and the positive active material layer 2. Punchingmetals, expanded metals, and metallic foils with a lot of openings whichare formed by etching can preferably be used as the above porous metalfoil.

Materials used as the positive active material of the positive activematerial layer 2 depend on the type of the battery, and can includemetallic oxides, metal sulfides, specific high molecular materials, andlithium composite oxides that are expressed by a general formula such asLi_(x)MO₂, for example. Here, in the above general formula, M is one ormore kinds of transition metals, and X is usually a value in a range of0.05≦X≦1.12. Moreover, at least one kind of Co (cobalt), Ni (nickel),and Mn (manganese) is applicable as the transition metal M, for example.In addition, a general synthetic resin material or the like issufficient as a binder used in order to form the positive activematerial layer 2.

The negative electrode laminate 6 is formed by applying the negativeactive material layer 3 containing a negative electrode active materialto both sides of a negative electrode current collector 16 as shown inFIG. 5, for example.

Copper foil or nickel foil can preferably be used as the negativeelectrode current collector 16, for example. The metallic foil isdesirably porous metal foil because of the same reason in the case ofthe positive electrode current collector 15. Moreover, punching metals,expanded metals, and metallic foils with a lot of openings which areformed by etching can preferably be used as the above porous metal foillike the case of the positive electrode current collector 15.

Lithium metals, alloys of a lithium metal and other metal, or carbonmaterials can preferably be used as the negative electrode activematerial of the negative active material layer 3, for example. Morespecifically, materials used as the carbon material can include naturalgraphite, artificial graphite, non-graphitizable carbon, pyrolyticcarbons, cokes (for example, pitch coke, needle coke, petroleum coke),carbon blacks such as acetylene black, glassy carbon, activated carbon,carbon fiber, organic high molecular heat treated object obtained bysintering an organic high molecular compound such as cellulose, a phenolresin, or a furan resin.

Microporous thin film, which contains a polyolefin such aspolypropylene, polyethylene, or a composite thereof as a principalcomponent, can preferably be used as the separator 1, for example. It ismore preferable to use microporous thin films having wettability to anelectrolyte which is improved by a surfactant or corona dischargeprocessing.

The porosity of the separator 1 is preferably a value in a range of30–60%, for example, but is not necessarily limited to this. This isbecause there are tendencies that the porosity less than 30% of theseparator 1 decreases remarkably output characteristics of the battery,and that the porosity more than 60% decreases remarkably mechanicalstrength of the separator 1 itself. This is not to say that the porosityis not necessarily limited to such a numeric range. For example, inorder to further improve the output characteristics of the battery, theporosity of 70% can be permitted despite of reduction of the mechanicalstrength. Moreover, an average pore size of holes of the separator 1 ispreferably 1 micrometer or less in order to prevent an internal shortcircuit and generate a shutdown action by hole blockage moreeffectively, but is not necessarily limited to this. Moreover, thicknessof the separator 1 is desirably a value in a range of 5–35 micrometers,for example. More desirably, the thickness may be set to a value in arange of 7–25 micrometers in light of interrelation between themechanical strength of the separator 1 and electric resistance, but thisis not to say that the value is not necessarily limited to such a range.

Materials preferably used as the nonaqueous electrolyte can includegel-like electrolytes where a nonaqueous electrolytic solution, which isproduced by dissolving an electrolyte salt in a nonaqueous solvent, isgelated with a matrix polymer. LiPF₆, LiClO₄, LiCF₃SO₃, LiAsF₆, LiBF₄,LiN (CF₃SO₃)₂, C₄F₉SO₃Li, a mixture thereof, and the like can be used asthe electrolyte salt used for the nonaqueous electrolyte. Of thesematerials, LiPF₆ is desirably used in light of ion conductivity.Moreover, an added amount of the electrolyte salt is desirably in arange of 0.1–2.0 mol/l (a mol/liter) of a concentration to thenonaqueous solvent in order to obtain good ion conductivity, but this isnot to say that the electrolyte salt is not necessarily limited to theabove materials and numerical range.

Polyacrylonitrile and copolymers of polyacrylonitrile can be used as apolymeric material which is used for the gel-like electrolyte, forexample. Copolymerized monomers (vinyl monomers) thereof can includevinyl acetate, methyl methacrylate, butyl methacrylate, methyl acrylate,butyl acrylate, itaconic acid, methyl acrylate hydride, ethyl acrylatehydride, acrylamide, vinyl chloride, vinylidene fluoride, vinylidenechloride, for example. In addition, acrylonitrile butadiene rubber,acrylonitrile styrene-butadiene resin,acrylonitrile-polyethylene-chloride-propylene-diene-styrene resin,acrylonitrile vinyl chloride resin, acrylonitrile methacrylate resin,acrylonitrile acrylate resin, and the like can also be used. Also,polyethylene oxide and copolymers of polyethylene oxide can be used asthe polymeric material which is used for the gel-like electrolyte.Copolymerized monomers thereof can include polypropylene oxide, methylmethacrylate, butyl methacrylate, methyl acrylate, butyl acrylate, forexample. Polyvinylidene fluoride and copolymers of polyvinylidenefluoride can also be used as the polymeric material which is used forthe gel-like electrolyte, and copolymerized monomers thereof can includehexafluoropropylene, tetrafluoroethylene, for example. In addition, oneof these materials or a mixture of two or more thereof can be used asthe polymeric material which is used for the gel-like electrolyte. It ismore preferable that the gel-like electrolyte is formed using a highmolecular compound consisting of a copolymer of polyvinylidene fluorideand polyhexafluoropropylene, and the nonaqueous electrolyte. Thisprovides a gel-like electrolyte with high mechanical strength.

An aluminum thin plate which is processed into a strip shape with acertain dimension can be used as the positive lead electrode 8, forexample. Also, a thin plate of a nickel alloy which is processed in astrip shape with a certain dimension can be used as the negative leadelectrode 9, for example.

The positive lead electrode 8 is joined to a certain position of an endof the innermost surface of the positive electrode laminate 5 withwelding or the like. The negative lead electrode 9 is joined to acertain position of an end of the innermost surface of the negativeelectrode laminate 6 with soldering, spot welding or the like.

Here, the wound structure shown in FIG. 1 is set so that the positiveelectrode laminate 5 may be located in an outermost periphery of thewound electrode 4. In this case, the positive active material layer 2 isnot applied to an almost entire outermost periphery of an outsidesurface of the positive electrode laminate 5 in the outermost peripheryof the wound electrode 4 (that is, an outside surface of the outermostperiphery of the wound electrode 4), where the positive electrodecurrent collector 15 is exposed. If the active material layer exists inthe outermost periphery, it has substantially no contribution toelectromotive as a battery. Thus such a useless part is eliminated asdescribed above, which provides achievement of further reducing a volumeand weight of the battery. Also, for the same purpose, the positiveactive material layer 2 is not applied to a position where the positivelead electrode 8 is located on the positive electrode current collector15, and the negative active material layer 3 is not also applied to aposition where the negative lead electrode 9 is located in the negativeelectrode current collector 16. The positive lead electrode 8 and thenegative lead electrode 9 have joint parts with such a structure, whichprovides also an effect of obtaining a flatter outer shape of the woundelectrode 4.

Any film or thin plate having damp proofing is usable as a formationmaterial of the exterior container 10, and, for example, an exteriormaterial film with a three-layer structure, where a nylon film, aluminumfoil, and a polyethylene film are laminated in this order, canpreferably be used.

The lithium ion secondary battery with the above schematic structure isproduced as follows.

First, the positive electrode laminate 5 and the negative electrodelaminate 6 having the laminated structures as described above areproduced. Specifically, powder of the positive active material such asthe above material is homogeneously mixed, if needed, with conductivereinforcing agent like carbon black or graphite, and a binding agentlike polyvinylidene fluoride. And a solvent such as dimethylformaldehyde or n-methyl pyrolidone and other additives are added toprepare a paste-like positive electrode mixture. Then, the mixture isuniformly applied to both sides of the positive electrode currentcollector 15 composed of a processed aluminum thin plate, and is driedto form the positive active material layer 2. Here, the positive activematerial layer 2 is not intentionally applied to the certain position ofthe end which is set to be located near the innermost side of the woundelectrode 4 in the positive electrode laminate 5, in order to provide abonding part for joining the positive lead electrode 8 where the surfaceof the positive electrode current collector 15 is exposed. The positiveactive material layer 2 is not intentionally applied to an part which isset to be located in the almost entire outermost periphery of the woundelectrode 4 in the positive electrode laminate 5 to provide a spacewhere the outside surface of the positive electrode current collector 15is exposed, in order to reduce the volume and weight of the useless partwhich has no contribution to the electromotive. Then, the positive leadelectrode 8 is joined to the bonding part.

In such a way, the positive electrode laminate (the positive electrode)5 as shown in FIG. 4 can be produced.

In addition, in the case of the secondary battery using a gelelectrolyte layer, which is not shown, it is also desirable that a solelectrolyte, where a nonaqueous electrolyte is dissolved in an addedmatrix polymer, is applied to a surface of the positive active materiallayer 2 and cooled for curing, in order to further laminate and form thegel electrolyte layer.

On the other hand, for forming the negative electrode laminate 6, powderof the negative active material such as the above material is uniformlymixed with a binding agent like polyvinylidene fluoride, and further asolvent such as dimethyl formaldehyde or n-methyl pyrolidone, anadditive, and the like are added to prepare a paste-like negativeelectrode mixture. And the mixture is uniformly applied to both sides ofthe negative electrode current collector 16 composed of a processednickel alloy thin plate, and is dried to form the negative activematerial layer 3. Here, the negative active material layer 3 is notintentionally applied to the certain position of the end which is set tobe located near the innermost side of the wound electrode 4 in thenegative electrode laminate 6, in order to provide a bonding part forjoining the negative lead electrode 9 where the surface of the negativeelectrode current collector 16 is exposed. Then, the negative leadelectrode 9 is joined to the bonding part.

In such a way, the negative electrode laminate (the negative electrode)6 as shown in FIG. 5 can be produced.

In addition, in the case of the secondary battery using the gelelectrolyte layer, which is not shown, it is also desirable that a solelectrolyte, where a nonaqueous electrolyte is dissolved in an addedmatrix polymer, is applied to a surface of the negative active materiallayer 3 and cooled for curing, in order to further laminate and form thegel electrolyte layer. It is also desirable to apply a sol-likeelectrolyte and cool it for curing to laminate and form the gelelectrolyte layer.

The negative electrode laminate 6 and the positive electrode laminate 5are produced as described above, and those and the separator 1 areimpregnated with the nonaqueous electrolytic liquid (or thisimpregnation may be performed after forming the wound electrode 4).After that, the jig 21 for the winding which is plate-like and has theslit (gap) 20 in a position of a rotation center for holding theseparator 1 therethrough is prepared like an example shown in FIG. 6.

And the separator 1 is inserted through the slit 20 of the jig 21, andthe approximate center part 7 of the separator 1 is pinched through theslit 20 of the jig 21 with moderate force as shown in FIG. 7A.

Then, as shown in FIG. 7B, moderate soft tensile force is leftwardsapplied to a left half area from the center part 7 of the separator 1which is pinched by the slit 20 of the jig 21, and moderate soft tensileforce is rightwards applied to a right half area from the center part 7of the separator 1. The positive electrode laminate 5 is insertedbetween the lower surface (the first area) of the left half area fromthe center part 7 of the separator 1 and a upper surface 22 on the leftof the slit 20 of the jig 21, and the negative electrode laminate 6 isinserted between the upper surface (the second area) of the right halfarea from the center part 7 of the separator 1 and a lower surface 23 onthe right of the slit 20 of the jig 21.

Then, as shown in FIG. 7C, tensile force with moderate strength isapplied to right and left of the separator 1 without damaging theseparator 1 to surely hold the innermost ends of the positive electrodelaminate 5 and the negative electrode laminate 6 between the jig and theseparator 1. Then, the jig is rotated in the right direction (clockwiserotation) on a rotation axis 24 which is located in alignment with theslit 20, and the separator 1, the positive electrode laminate 5, and thenegative electrode laminate 6 are wound around the jig 21 and bound toit, as shown in FIG. 7D. After finishing the winding, the jig 21 isremoved from the wound electrode 4 to complete the wound electrode 4.

This provides the wound electrode 4 sufficiently with the flat shape,and if needed, moderate press force may further be applied from theupper and lower surfaces of the wound electrode 4 to accomplish moreperfect flat shape.

The wound electrode 4 as shown in FIG. 1 can be produced as describedabove. In the wound electrode 4 which is wound by such a procedure,compared with the conventional case (which is not shown) of using a corecomposed of a wound end of the separator 1, or a core material for acenter part, the core and the core material is eliminated, and thevolume and weight corresponding to them can be reduced. Consequently,the reducing the thickness of the secondary battery, for example, to 160μm can be accomplished maintaining the same discharge capacity can beaccomplished. Furthermore, the winding using the plate-like jig 21provides the formation of the wound electrode 4 with the flat shapesimultaneously in the winding step, which can avoid or eliminatedistortion and stress (residual stress) in terms of strength of materialwhich is generated in a process of performing of press working of thewound electrode into the flat shape with the even thickness with theconventional technique.

The wound electrode 4 produced as described above is housed in theexterior container 10, and the periphery part of the flat lid 11 and theflange part 13 around the container body 12 are bonded and sealed withthermocompression bonding or the like. At this time, both of thepositive lead electrode 8 and the negative lead electrode 9, whichproject from the wound electrode 4, project out from one end of theexterior container 10. And the electric insulating resin films 14 aredisposed respectively on the parts of the positive lead electrode 8 andthe negative lead electrode 9 which are between the periphery part ofthe flat lid 11 and the flange part 13 around the container body 12.This is because when the electric insulating resin films 14 are disposedin the parts where the exterior container 10 may be contacted with thepositive lead electrode 8 and the negative lead electrode 9, an electricshort circuit or the like due to the metal weld flash of the laminatefilm which is the formation material of the exterior container 10 cansurely be prevented, and the sealing performance and the adhesiveness inthe parts where the positive lead electrode 8 and the negative leadelectrode 9 project out from the exterior container 10 can be obtainedmore surely.

Furthermore, the separator 1 is not limited to one seamless piece, andmay be composed of segments which are separated by the center part 7(the center position for the winding). Namely, a wound electrode 27 asshown in FIG. 9 may be produced by forming completely separated twosheets, which respectively have a laminate of a separator 1 a and thepositive electrode laminate 5 on the first area (the left half area inthe figure) and a laminate of a separator 1 b and the negative electrodelaminate 6 on the second area (the right half area in the figure), andfor example, holding the sheets between two jigs 25 and 26 such as anexample shown in FIG. 8, winding the sheets and removing the jigs 25 and26 after finishing the winding.

In such a case, it should be noticed that ends of the positive electrodelaminate 5 and the negative electrode laminate 6 face substantially eachother in the center part 7 as shown in FIG. 10, so the end of thepositive electrode laminate 5 may be contacted with the end of thenegative electrode laminate 6 as shown in FIG. 11 and an electricalshort circuit may occur, when the wound electrode 27 is pressed, or whenthe press force is applied to it from the exterior. Therefore, in orderto prevent such an electrical short circuit, for example, it isdesirable to cover the ends of the positive electrode laminate 5 and thenegative electrode laminate 6 with ends of the separator 1 a and theseparator 1 b like an example as shown in FIG. 12. Or the ends of thepositive electrode laminate 5 and the negative electrode laminate 6 maybe covered with insulating tapes 28 a and 28 b like an example as shownin FIG. 13.

Alternatively, the two separators 1 a and 1 b may be bonded each otheras shown in FIG. 14, or the two separators 1 a and 1 b may be bondedeach other, for example, with adhesive tapes 40 a and 40 b as shown inFIG. 15, in order to form substantially one piece separator which can beused as the above separator 1.

In the above embodiment, the case where the technique of this inventionis applied to the flat type lithium ion secondary battery has beendescribed, but other shape such as a square shape can be used as theouter shape of the battery.

Moreover, the structure where the positive lead electrode 8 and thenegative lead electrode 9 are located on the innermost side of the woundelectrode 4 has been described in the above embodiment, but they may belocated on the outermost periphery. Alternatively, one of the positivelead electrode 8 and the negative lead electrode 9 may be located on theoutermost periphery, and the other may be located on the innermostperiphery.

Moreover, each of the positive electrode laminate and the negativeelectrode laminate is composed of the active material which is appliedto both sides of one piece of the current collector in the aboveembodiment. In addition to this, for example, like an example as shownin FIG. 16, plurality of the positive electrode laminates 5 and thenegative electrode laminates 6, where each has the active material beingapplied to both sides of one piece of the current collector, areprepared, the plurality of the positive electrode laminates 5 arelaminated to form a multilayer positive electrode laminate 29, theplurality of the negative electrode laminates 6 are laminated to form amultilayer negative electrode laminate 30, and these multilayer positiveelectrode laminate 29 and multilayer negative electrode laminate 30 arerespectively inserted into parts between one piece of the separator 1and the jig 21, and are wound.

Moreover, this is not to say that the lithium ion secondary batterydescribed in the above embodiment may be used like primary batteries.

As described above, according to the nonaqueous electrolyte battery andthe method for manufacturing the nonaqueous electrolyte battery of theinvention, the positive electrode having the positive active materiallayer is located in the first area which extends from the approximatecenter part to one end on one of both sides of the separator, thenegative electrode having the negative active material layer is locatedin the second area which extends from the approximate center part to theother end on the other side of the separator which is opposite to oneside of both sides of the separator, and the separator having thepositive electrode and the negative electrode thereon is wound aroundthe approximate center part to obtain the wound electrode. Therefore,the core composed of the wound end of the separator, the core materialsas another component, and the like are unnecessary for the approximatecenter part of the wound electrode, and the useless part which has nocontribution to the electromotive can further be reduced, and higherenergy density can be accomplished.

Moreover, according to the nonaqueous electrolyte battery and the methodfor manufacturing the nonaqueous electrolyte battery of one aspect ofthe invention, the positive electrode is composed of the positive activematerial layer being applied to the positive electrode currentcollector, and the negative electrode is composed of the negative activematerial layer being applied to the negative electrode currentcollector, the part, to which neither positive active material layer nornegative active material layer is applied, may be located at theoutermost periphery of the wound electrode. This can eliminate theactive material layer on the outermost periphery of the wound electrode,which has no contribution to the electromotive, and reduce further thevolume of the part corresponding thereto, resulting in theaccomplishment of the higher energy density.

Moreover, according to the nonaqueous electrolyte battery and the methodfor manufacturing the nonaqueous electrolyte battery of another aspectof the invention, the lead electrode is located in the certain position,which is on the innermost part near the approximate center part of thewound electrode, on the positive electrode and/or the negativeelectrode, the positive electrode is composed of the positive activematerial layer being applied to the positive electrode currentcollector, and the negative electrode is composed the negative activematerial layer being applied to the negative electrode currentcollector, neither positive active material layer nor negative activematerial layer is applied to the position of the lead electrode. Thiscan eliminate the part which has substantially no contribution to theelectromotive, reduce further the volume of the above part, and preventthe occurrence of irregularity of the wound electrode due to thethickness of the lead electrode.

Moreover, according to the nonaqueous electrolyte battery and the methodfor manufacturing the nonaqueous electrolyte battery of still anotheraspect of the invention, the nonaqueous electrolyte is the gel-likeelectrolyte, so electromotive properties and the discharge capacityitself can be improved further.

Moreover, according to the nonaqueous electrolyte battery and the methodfor manufacturing the nonaqueous electrolyte battery of still anotheraspect of the invention, using the flat plate-type jig having the slitin the center thereof which the separator is held through, theapproximate center part of the separator is tightly held through theslit, the separator is wound and bound around the jig to form the woundelectrode and the jig is removed from the wound electrode after thewinding. This allows the wound electrode with the flat shape to beformed simultaneously in the winding step, and which can avoid oreliminate distortion and stress (residual stress) in terms of strengthof material which is generated in the process of processing it into theflat shape having the even thickness with the conventional technique.

Obviously many modifications and variations of the present invention arepossible in the light of the above description. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

1. A nonaqueous electrolyte battery comprising: a wound electrodeassembly and a non aqueous electrolyte, wherein the wound electrodeassembly comprises: a separator impregnated with the nonaqueouselectrolyte, a positive electrode connected to a positive lead electrodehaving a positive active material layer located in a first area of thewound electrode assembly, a negative electrode connected to a negativelead electrode having the negative active material layer located in asecond area of the wound electrode assembly, and a center part betweenthe first area and second area around which the separator is wound,wherein, the first area extends from the center part toward a first endof the wound electrode assembly on a first side of the separator, thesecond area extends from the center part toward a second end of thewound electrode assembly on a second side of the separator, the woundelectrode assembly is covered with an exterior material comprising ashaped laminate film of a synthetic resin and metallic foil, thepositive lead electrode and the negative lead electrode are exposedthrough the exterior material, and a resin film is located in parts ofthe positive lead electrode and the negative lead electrode.
 2. Anonaqueous electrolyte battery according to claim 1, wherein thepositive electrode is composed of the positive active material layerbeing applied to a positive electrode current collector, the negativeelectrode is composed of the negative active material layer beingapplied to a negative electrode current collector, and neither positiveactive material layer nor negative active material layer is applied toan outermost periphery of the wound electrode assembly.
 3. A nonaqueouselectrolyte battery according to claim 1, wherein a lead electrode islocated in a certain position, which is on an innermost part near thecenter part of the wound electrode assembly, of the positive electrodeand/or the negative electrode.
 4. A nonaqueous electrolyte batteryaccording to claim 3, wherein the positive electrode is composed of thepositive active material layer being applied to a positive electrodecurrent collector, the negative electrode is composed of the negativeactive material layer being applied to a negative electrode currentcollector, and neither positive active material layer nor negativeactive material layer is applied to a position of the lead electrode. 5.A nonaqueous electrolyte battery according to claim 1, wherein thenonaqueous electrolyte is a gel electrolyte.
 6. A nonaqueous electrolytebattery according to claim 1, wherein the separator has a first segmentand a second segment which are separated by the center part, wherein thepositive electrode on the first area and the negative electrode on thesecond area are respectively laminated, and the first segment almostfaces the second segment.
 7. A nonaqueous electrolyte battery accordingto claim 6, wherein, at least one of the ends of the segments facingeach other in the center part is covered with the separator or aninsulating material.
 8. A method for manufacturing a nonaqueouselectrolyte battery which comprises a wound electrode assembly where onesubstantially seamless separator, a positive electrode having a positiveactive material layer, and a negative electrode having a negative activematerial layer are wound, and a nonaqueous electrolyte with which atleast the separator is impregnated, comprising the steps of: locatingthe positive electrode having the positive active material layer in afirst area which extends from a center part to a first end of the woundelectrode assembly on a first side of the separator; locating thenegative electrode having the negative active material layer in a secondarea which extends from the center part to a second end of the woundelectrode assembly on a second side of the separator; and winding theseparator which has the positive electrode and the negative electrodethereon around the center part to form the wound electrode assembly. 9.A method for manufacturing a nonaqueous electrolyte battery according toclaim 8, wherein the positive active material layer is applied to apositive electrode current collector to form the positive electrode, thenegative active material layer is applied to a negative electrodecurrent collector to form the negative electrode, and neither positiveactive material layer nor negative active material layer is applied toan outermost periphery of the wound electrode assembly.
 10. A method formanufacturing a nonaqueous electrolyte battery according to claim 8,wherein a lead electrode is located in a certain position, which is onan innermost part near the innermost center part of the wound electrodeassembly, of the positive electrode and/or the negative electrode.
 11. Amethod for manufacturing a nonaqueous electrolyte battery according toclaim 10, wherein the positive active material layer is applied to apositive electrode current collector to form the positive electrode, thenegative active material layer is applied to a negative electrodecurrent collector to form the negative electrode, and neither positiveactive material layer nor negative active material layer is applied to aposition of the lead electrode.
 12. A method for manufacturing anonaqueous electrolyte battery according to claim 8, wherein a gelelectrolyte is used as the nonaqueous electrolyte.
 13. A method formanufacturing a nonaqueous electrolyte battery according to claim 8,wherein the separator is separated into a first segment and a secondsegment at the center part before winding the separator, on which thepositive electrode on the first area and the negative electrode on thesecond area are respectively laminated, an end of the first segment andan end of the second segment are located to almost face each other, andthe first and second segments are wound around the center part to formthe wound electrode assembly.
 14. A method for manufacturing anonaqueous electrolyte battery according to claim 13, wherein at leastone of the ends of the segments facing each other in the center part iscovered with the separator or an insulating material.
 15. A method formanufacturing a nonaqueous electrolyte battery according to claim 8,wherein using a jig having a slit in a center thereof which theseparator is held through, the center part of the separator is tightlyheld through the slit, the separator is wound and bound around the jigto form the wound electrode assembly and the jig is removed from thewound electrode assembly after the winding.
 16. A nonaqueous electrolytebattery comprising: a wound electrode assembly and a non aqueouselectrolyte, wherein the wound electrode assembly comprises: a separatorimpregnated with the nonaqueous electrolyte, a positive electrode havinga positive active material layer located in a first area of the woundelectrode assembly, a negative electrode having the negative activematerial layer located in a second area of the wound electrode assembly,and a center part between the first area and second area around whichthe separator is wound, wherein, the first area extends from the centerpart toward a first end of the wound electrode assembly on a first sideof the separator, and the second area extends from the center parttoward a second end of the wound electrode assembly on a second side ofthe separator.